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Events on Friday, February 5th, 2010

Theory/Phenomenology Seminar
Holography and the Speed of Sound at High Temperature
Time: 2:30 pm
Place: 5280 Chamberlin Hall
Speaker: Paul Hohler, University of Illinois at Chicago
Abstract: An expression for the speed of sound will be formulated in a general class of strongly interacting theories using holographic techniques. Using this expression, it can be shown that for this class of theories at high temperatures the speed of sound approaches the conformal value cs2=1/3 universally from below. This class includes theories holographically dual to a theory of gravity coupled to a single scalar field, representing the operator of the scale anomaly.
Host: Sogee Spinner
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SPECIAL ASTRONOMY TALK
Breaching the Eddington Limit in the Most Massive, Most Luminous Stars"
Time: 2:30 pm
Place: 3425 Sterling Hall
Speaker: Professor Stan Owocki, University of Delaware
Abstract: Basic stellar structure dictates that stars of ca. 100 Msun or more will be close to the Eddington limit, with luminosities in excess of 106 Lsun, and radiation pressure contributing prominently to interior support against gravity. Although it is formally possible to generate static structure models of even more massive stars, extensive observational surveys of massive stellar clusters suggest an upper stellar mass limit of ca. 140 Msun. This talk will focus on the role of extreme mass loss in limiting the masses of stars, emphasizing in particular that continuum driving, possibly associated with structural instabilities of radiation dominated envelope, can lead to much stronger mass loss than is possible by the usual line-scattering mechanism of steady stellar winds. I will also discuss the implications for the evolution of the most massive stars, including Luminous Blue Variables (LBVs), the first stars and GRB progenitors.
Host: Prof Richard Townsend
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